The present invention relates to emulsions used for medicine, food and the like, more particularly to fatty emulsions stabilized by polysaccharide derivatives which can embed fat-soluble substances in large quantities.
As medicine carriers, albumin, fibrinogen, erthrocyte ghost, gelatin, starch, polylactide, polyglycoride, dextran, polyethyl carbonate, liposome, emulsions and the like have been found. In these materials, liposome and O/W emulsions are hopeful.
It is well-known that, when the surface of liposome is coated with a polysaccharide derivative by their mutual interaction of non-covalent bonds, the structure of liposome is stabilized. (Japanese Laid-Open Patent Publication Nos. 58-49311 and 61-69801).
Lately, as mentioned above, liposome and O/W emulsions are hopeful as medicine carriers. Among them, liposome has disadvantages which are the lack of chemical and mechanical stabilities and the difficulty of long-term preservation. The present inventors found that the structure stability of liposome was considerably improved by coating the surface of liposome with a polysaccharide. However, a satisfactory stability is not yet obtained. The other hand, an O/W emulsion comprising of lecithin, oil and water is excellent as a carrier of fat-soluble medicines because it is possible to embed them in large quantities. Furthermore, fatty emulsions (lipid microsphere) has been conventionally prepared by emulsifying oil with phospholipids of negative electric charge for obtaining the colloid stability. When the surface electric charge of particles is neutralized by the presence of calcium ions and the like, the embedding of fat-soluble medicines, the pH change in the system, etc., these fatty emulsions tend to associate or aggregate. Accordingly, there are problems in regard of the colloid stability.
The present inventors have conducted research for resolving the above problems and for stably emulsifying oil with emulsions other than phospholipids and they have found that oil is stably emulsified by using polysaccharide derivatives which can efficiently improve the structure stability of liposome. Then, they have found fatty emulsions stabilized by polysaccharide derivatives.